The present invention relates to the extrusion of masses through an extrusion duct (die) having an outlet end of predetermined diametral dimensions, in which the mass to be extruded is forced into the duct and emerges from the outlet end of the extrusion duct in the extruded state in a generally-axial direction relative to the extrusion duct itself.
FIG. 1 of the appended drawings illustrates schematically, in axial section, an extrusion device operating according to the prior art. In this case the mass which is being extruded is generally indicated M. The extrusion duct or die is indicated 1 and its outlet end, centred around the principal axis 2 of the duct 1, is indicated 3.
The means which allow the necessary pressure to be exerted on the mass M to be extruded to force it into the extrusion duct 1 are considered to be generally known. Furthermore, their structure and configuration are not relevant per se, either for an understanding of the technical problem on which the invention is based, or for an understanding of the solution according to the invention.
The Applicant has noticed that, when an extrusion structure of the type illustrated in FIG. 1 is used to extrude an edible, pasty mass, such as a mixture of sugar and pectin, with quite a high linear extrusion velocity, for example of the order of 10-15 m/min or more, deformation of the extruded mass occurs, causing it to move away from the principal axis 2 of the extrusion duct 1, as illustrated schematically in the lower part of FIG. 1.
This occurs even when the extrusion is carried out vertically, that is with the duct 1 held with its principal axis 2 disposed vertically. Without wishing to tie himself to any specific theory in this regard, the Applicant has reason to believe that the bending of the extruded mass can be attributed essentially to the manifestation of localised adhesion of the external walls of the extruded mass to the edge of the end 3 of the extrusion duct 1.
In any case, the bending of the extruded mass is such that, when the mass is subsequently divided into pieces by a cutting operation, carried out, for example, with a rotary blade, the pieces obtained are generally curved in shape, or, so to speak, bean- or banana-shaped.
This problem is particularly serious when the pieces obtained from the extruded mass are intended to be coated subsequently in order to form products of the type generally known as "dragees".
For example, the coated product sold by the Applicant under the Trade name "TIC-TAC" includes a centre produced from a mixture of sugar and pectin, having a cylindrical shape with a length of approximately 9 mm and a diameter of approximately 2 mm. Up to now, a moulding process has had to be used to make these centers, as it has not been possible -- for the reasons explained above -- to use a method of extrusion and subsequent cutting.